/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.config.annotation;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.HandshakeHandler;
import org.springframework.web.socket.server.HandshakeInterceptor;
import org.springframework.web.socket.server.support.DefaultHandshakeHandler;
import org.springframework.web.socket.server.support.OriginHandshakeInterceptor;
import org.springframework.web.socket.sockjs.SockJsService;
import org.springframework.web.socket.sockjs.transport.handler.WebSocketTransportHandler;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Base class for {@link WebSocketHandlerRegistration WebSocketHandlerRegistrations} that gathers all the configuration
 * options but allows sub-classes to put together the actual HTTP request mappings.
 *
 * @param <M> the mappings type
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @since 4.0
 */
public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSocketHandlerRegistration {

    private final MultiValueMap<WebSocketHandler, String> handlerMap = new LinkedMultiValueMap<>();
    private final List<HandshakeInterceptor> interceptors = new ArrayList<>();
    private final List<String> allowedOrigins = new ArrayList<>();
    @Nullable
    private HandshakeHandler handshakeHandler;
    @Nullable
    private SockJsServiceRegistration sockJsServiceRegistration;


    @Override
    public WebSocketHandlerRegistration addHandler(WebSocketHandler handler, String... paths) {
        Assert.notNull(handler, "WebSocketHandler must not be null");
        Assert.notEmpty(paths, "Paths must not be empty");
        this.handlerMap.put(handler, Arrays.asList(paths));
        return this;
    }

    @Override
    public WebSocketHandlerRegistration setHandshakeHandler(@Nullable HandshakeHandler handshakeHandler) {
        this.handshakeHandler = handshakeHandler;
        return this;
    }

    @Nullable
    protected HandshakeHandler getHandshakeHandler() {
        return this.handshakeHandler;
    }

    @Override
    public WebSocketHandlerRegistration addInterceptors(HandshakeInterceptor... interceptors) {
        if (!ObjectUtils.isEmpty(interceptors)) {
            this.interceptors.addAll(Arrays.asList(interceptors));
        }
        return this;
    }

    @Override
    public WebSocketHandlerRegistration setAllowedOrigins(String... allowedOrigins) {
        this.allowedOrigins.clear();
        if (!ObjectUtils.isEmpty(allowedOrigins)) {
            this.allowedOrigins.addAll(Arrays.asList(allowedOrigins));
        }
        return this;
    }

    @Override
    public SockJsServiceRegistration withSockJS() {
        this.sockJsServiceRegistration = new SockJsServiceRegistration();
        HandshakeInterceptor[] interceptors = getInterceptors();
        if (interceptors.length > 0) {
            this.sockJsServiceRegistration.setInterceptors(interceptors);
        }
        if (this.handshakeHandler != null) {
            WebSocketTransportHandler transportHandler = new WebSocketTransportHandler(this.handshakeHandler);
            this.sockJsServiceRegistration.setTransportHandlerOverrides(transportHandler);
        }
        if (!this.allowedOrigins.isEmpty()) {
            this.sockJsServiceRegistration.setAllowedOrigins(StringUtils.toStringArray(this.allowedOrigins));
        }
        return this.sockJsServiceRegistration;
    }

    protected HandshakeInterceptor[] getInterceptors() {
        List<HandshakeInterceptor> interceptors = new ArrayList<>(this.interceptors.size() + 1);
        interceptors.addAll(this.interceptors);
        interceptors.add(new OriginHandshakeInterceptor(this.allowedOrigins));
        return interceptors.toArray(new HandshakeInterceptor[0]);
    }

    /**
     * Expose the {@code SockJsServiceRegistration} -- if SockJS is enabled or
     * {@code null} otherwise -- so that it can be configured with a TaskScheduler
     * if the application did not provide one. This should be done prior to
     * calling {@link #getMappings()}.
     */
    @Nullable
    protected SockJsServiceRegistration getSockJsServiceRegistration() {
        return this.sockJsServiceRegistration;
    }

    protected final M getMappings() {
        M mappings = createMappings();
        if (this.sockJsServiceRegistration != null) {
            SockJsService sockJsService = this.sockJsServiceRegistration.getSockJsService();
            this.handlerMap.forEach((wsHandler, paths) -> {
                for (String path : paths) {
                    String pathPattern = (path.endsWith("/") ? path + "**" : path + "/**");
                    addSockJsServiceMapping(mappings, sockJsService, wsHandler, pathPattern);
                }
            });
        } else {
            HandshakeHandler handshakeHandler = getOrCreateHandshakeHandler();
            HandshakeInterceptor[] interceptors = getInterceptors();
            this.handlerMap.forEach((wsHandler, paths) -> {
                for (String path : paths) {
                    addWebSocketHandlerMapping(mappings, wsHandler, handshakeHandler, interceptors, path);
                }
            });
        }

        return mappings;
    }

    private HandshakeHandler getOrCreateHandshakeHandler() {
        return (this.handshakeHandler != null ? this.handshakeHandler : new DefaultHandshakeHandler());
    }


    protected abstract M createMappings();

    protected abstract void addSockJsServiceMapping(M mappings, SockJsService sockJsService,
                                                    WebSocketHandler handler, String pathPattern);

    protected abstract void addWebSocketHandlerMapping(M mappings, WebSocketHandler wsHandler,
                                                       HandshakeHandler handshakeHandler, HandshakeInterceptor[] interceptors, String path);

}
